Leukotrienes (LTs) are products of arachidonic acid metabolism derived through the 5-lipoxygenase pathway. The initial step in LT production involves oxygenation of arachidonic acid to produce 5-hydroperoxyeicosatetranoic acid and a subsequent dehydrase step to produce the epoxide intermediate, LTA.sub.4, both enzymic steps being catalyzed by 5-lipoxygenase in association with a 5-lipoxygenase activating protein. Two routes of metabolism of LTA.sub.4 lead to the production of biologically active products. LTA.sub.4 hydrolase catalyses the stereoselective hydrolysis of LTA.sub.4 to produce the dihydroxy fatty acid, LTB.sub.4. LTB.sub.4 interacts with high-affinity receptor sites to induce leukocyte and lymphocyte activation. A second pathway involves conjugation with glutathione to produce the peptidolipid conjugate, LTC.sub.4, this reaction being catalyzed by LTC.sub.4 synthase. LTC.sub.4 in turn is metabolized to LTD.sub.4 by .gamma.-glutamyl transpeptidase and then to LTE.sub.4 by a dipeptidase. In the human lung LTC.sub.4, LTD.sub.4, and LTE.sub.4 all interact with a high affinity LTD.sub.4 receptor.
Further details of the biosynthesis as well as the metabolism of the leukotrienes are to be found in the book Leukotrienes and Lipoxygenases, ed. J. Rokach, Elsevier, Amsterdam (1989). The actions of the leukotrienes in living systems and their contribution to various diseases states are also discussed in the book by Rokach.